The Flood is a non-sentient life form. That's why the Halo array is unable to kill it directly (the Flood is starved to death which is passive killing by Halo).
What I see about the Flood in the video game franchise:
- They recognize and attack all of their enemies; not just their food (sentient lives: humans, covenant), but also the Sentinels of 343 Guilty Spark.
- They handle advanced weapons like Plasma Guns, Shotguns, Rocket Launchers etc. Interestingly, they don't miss their target most of time.
- They operate advanced vehicles (of humans or covenant) very efficiently in coordination with other Flood beings.
- They create advanced plans to capture a spaceship so they can leave Halo.
- They fight with advanced team strategies.
How does they do all these things? Is there an intelligent collective or something similar for that?